1. Field of the Invention
The present invention relates generally to electrical switching apparatus and, more particularly, to an electrical switching apparatus including an operating handle and an interface assembly for activating the operating handle from a remote location. The invention also relates to operating handle attachments for electrical switching apparatus interface assemblies.
2. Background Information
Electrical switching apparatus include, for example, circuit switching devices and circuit interrupters, such as circuit breakers, contactors, motor starters, motor controllers and other load controllers.
Circuit breakers are generally old and well known in the art. An example of a circuit breaker is disclosed in U.S. Pat. No. 5,341,191. Circuit breakers are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition or a relatively high level short circuit or fault condition. Molded case circuit breakers, for example, include at least one pair of separable contacts which are operated either manually by way of a handle disposed on the outside of the case or automatically by way of an internal trip unit in response to an overcurrent condition.
Circuit breakers typically have two or three possible operating handle positions, corresponding to the status of the separable contacts. For example, these positions may include an ON position, in which the separable contacts are closed, an OFF position in which the contacts are open, and a tripped position in which the contacts are tripped open. Typically, the handle position corresponding to the tripped position of the contacts is in between the ON and OFF positions.
In certain applications, it is often desired or required to actuate the operating handle of the circuit breaker from a remote location. For example, circuit breakers are often mounted within the interior of a metal cabinet, such as a switchboard or panel board as part of an industrial power distribution system. See, e.g., U.S. Pat. No. 4,945,450. In motor control centers, the circuit breaker is typically contained within a cabinet, which is locked, in order to prevent access when the circuit breaker is ON and the electrical equipment within the cabinet is energized. When a circuit breaker is mounted in a remote location, for example, within the interior of a switchboard, a locked electrical cabinet or any other remote location, an externally accessible switching apparatus, such as an actuating handle, is employed to interface with the circuit breaker and actuate the breaker operating handle.
A relatively simple way to move the breaker handle from such remote locations is through use of a mechanical interface or linking assembly connecting the circuit breaker operating handle to the externally accessible actuating handle. In this manner, the circuit breaker can be actuated, for example, without having to open the cabinet. In such interfacing assemblies, effective operation relies heavily upon the secure engagement of the circuit breaker operating handle and a dependable linkage between the operating handle and the external actuating handle. For example, a linkage of insufficient strength or rigidity may not be capable of overcoming the resistive forces associated with moving the circuit breaker operating handle. Inadvertent separation of the circuit breaker operating handle from the interfacing linkage would require disassembly of the electrical cabinet to access the breaker and reattach the connection.
Interfacing assemblies employ a variety of circuit breaker operating handle extensions and actuating mechanisms having a wide array of operating handle engaging mechanisms. However, construction of the assemblies is typically complex, often comprising numerous, separate parts and frequently requiring modification to the circuit breaker operating handle and/or housing.
U.S. Pat. No. 3,142,744 discloses a switch operating attachment primarily for use by children too small to reach normally placed light switches, such as wall-mounted light switches. The attachment includes a mounting head with a rectangular counter bore for receiving the end of the light switch handle. A U-shaped spring is engaged endwise in the counter bore close to the bottom of the counter bore with the spring legs extending along the counter bore walls. The spring legs serve as spring jaws for gripping the upper and lower surfaces of the switch handle. The jaws are formed with longitudinally spaced gripping teeth or corrugations so that the teeth bite into and hold the switch handle secure within the head. The attachment further includes an elongated handle, which at one end, connects to a slot in the mounting head and at the other end extends far enough downwardly from the light switch handle to be within the reach of small children.
U.S. Pat. No. 4,626,638 discloses a mechanical operating system for operating a molded case circuit breaker from a remote position. The system is comprised of numerous complex components, including a master operating assembly and a slave operator for manipulating the circuit breaker handle. The master operating assembly is fixed at a location away from the circuit breaker and includes a handle connected to a flexible cable. The flexible cable is connected to a slave operator attached to the housing of the circuit breaker and includes an opening for encapturing the circuit breaker handle. Moving the handle of the master operating assembly displaces the slave operator and the circuit breaker handle encaptured therein.
U.S. Pat. No. 5,193,666 discloses a handle extender for a molded case circuit breaker including a remote actuator mechanism. The actuator cable is arranged in an endless loop between the actuator handle and the circuit breaker operating handle. Moving the actuator handle moves the circuit breaker operating handle. The remote actuator mechanism has numerous components including the actuator cable which includes an outer sheath and an inner flexible wire connected to the circuit breaker operating handle by a U-shaped plate. A fastener, which passes through the U-shaped plate and the operating handle, secures the flexible wire to the operating handle.
There is a need, therefore, for a simplified electrical switching apparatus interface assembly and operating handle attachment that effectively secures the operating handle for actuation from a remote location, without requiring modification to the electrical switching apparatus handle or housing.
Accordingly, there is room for improvement in electrical switching apparatus interface assemblies and in interface assemblies employing operating handle attachments.